The Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) is highly expressed in multiple cancers and inflammatory disorders where it stimulates secretion of matrix metalloproteinases (MMPs) and pro-inflammatory cytokines. EMMPRIN is amongst a subset of unique proteins that exist as a transmembrane protein but is released by cells in multiple uncharacterized forms. These extracellular forms have already been linked to at least half a dozen cancers and have been shown to contribute to a positive feedback loop during cancer progression. Thus, identifying the specific extracellular forms of EMMPRIN, characterizing how each of these forms contributes to disease progression, and identifying their cellular targets would significantly contribute to our understanding of cancer and inflammation. We have taken an integrative approach to fully characterize EMMPRIN and its role in disease progression by combining biological, biochemical, and atomic resolution studies. Our biological studies have already identified several extracellular forms of EMMPRIN in human blood and released by cancer cells that and the specific MMPs/cytokines secreted by these forms will be fully characterized here (Aim 1). To this end, we have developed recombinant expression systems that produce all the necessary proteins. We will then identify the cellular targets of these EMMPRIN forms by utilizing our recombinant proteins and characterize their interactions (Aim 2). Finally, we have begun solving the X-ray crystal structure and characterizing the solution behavior of a retinal-specific EMMPRIN isoform that contributes to retinoblastoma and here we will characterize this isoform both biophysically and biologically (Aim 3). Since EMMPRIN over-expression results in the deregulation of entire protein families integrally involved in the progression of multiple diseases, our combined biological and biophysical approach will fully characterize extracellular EMMPRIN at the biological and molecular levels, respectively. PUBLIC HEALTH RELEVANCE: Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) regulates many signaling pathways that become deregulated during dozens of cancers and inflammatory disorders, which include stimulating the secretion of MMPs and cytokines. Although EMMPRIN was initially identified as a cellular transmembrane protein, extracellular EMMPRIN has recently emerged as a central player in disease progression as well. However, little is known in regard to extracellular EMMPRIN and its interactions. We have discovered high levels of several extracellular EMMPRIN forms within human blood and we have already discovered that one of these is highly active. We have also established recombinant expression systems to produce all of these extracellular EMMPRIN forms that will allow us to characterize their activities here and we have initiated studies of a retinal-specific form of EMMPRIN that contributes to retinoblastoma. The proposed studies are focused on fully characterizing extracellular EMMPRIN forms in regard to their stimulatory activity of MMP/cytokine secretion and target interactions, providing insight into disease progression and the identification of novel therapeutic targets.